In processing substrates (for example semiconductor substrates--wafers) in vacuum chambers the temperature and variations in temperature of the vacuum chamber surfaces exposed to the substrate can and do affect the uniformity and quality of wafer processing. This is particularly true in vacuum chambers where chemical vapor disposition (CVD) of substrates occurs, where variations in temperature can affect the uniformity of a film layer deposited on the substrate or can cause flaking of film particles from the inside of the dome onto the substrate being processed as a result of differential thermal expansion.
In a processing chamber configuration as shown in FIG. 1, a substrate processing location 24 is located within a substrate vacuum processing chamber 20 and is surrounded by chamber walls 22 and covered by a ceramic dome 28. A series of arrows 36 show locations where processing gas enters the chamber. The vacuum system connection 26 provides for the gas exhaust once the gas has been depleted during processing. The chamber shown is commonly used for a plasma enhanced process where the high ceiling in the chamber provides generally uniform ion density at the surface of the substrate being processed at the substrate processing location 24. The gas, once it enters the processing chamber, is ionized by RF coils 30 in a coil framework 32 which is supported by a coil support member 34. The RF coils generate an electromagnetic field which ionizes the process gas creating a plasma with a generally uniform ion concentration at the substrate processing location 24. A variation in the temperature across the inside surface of the ceramic dome 28 can and does cause a variation in the thermal expansion of the dome and can cause any materials deposited on the inside surface of the dome to flake off during nonuniform heating and cooling.
To avoid negative effects as a result of the differential temperatures across the inside surface of the ceramic dome 28, a uniform temperature of the dome is desired. A cooling structure for use with a ceramic dome through which an RF coil generates a magnetic field must meet the requirements that it be transparent to the RF frequency field so that it does not affect the uniformity of ion concentration from the plasma generated from the RF coils so that the uniformity of ion concentration across the substrate being processed is not deleteriously affected by inclusion of such a cooling structure.